Computer help - pdf/Facebook virus??

My Mum was wondering why a memory stick she put into a digital photo frame wasn't displaying - kept just saying SETUP. She was adamant it had photos on it, I plugged it into my laptop, it said "view files" and sitting in there was some random PDF. I didn't open it, just showed her that there were no JPEGs there hence no picture. Did the "safely remove hardware" thing, pulled the memory stick.

Next thing, I've got Adobe Acrobat pop ups all over the place (clicked cancel, they'd come back, repeat) and when I tried to open Facebook it said account blocked due to sending spam, fill in details. The thing that got me was it asked for credit card details which FB never does.

Facebook via my phone and via this works laptop is fine so I suspect that my computer has somehow picked up a virus from this memory stick? Any ideas (given that my Norton antivirus is out of date... )

Acrobat is notorious for security holes that allow malware to infect. PDF files are the vector. Flash too. Adobe are now starting to do something about it, but have been slow.
Updating Reader is a good idea, as well as security 'ware.

No idea where it came from. I'm only staying here for a few days but in that time she'll usually me ask for help in sorting all her digital photos or whatever - that's fine obviously but she's got dozens of memory sticks lying round the place. They've been in and out of friends computers, hers, basically it could have come from anywhere...